Front Disk Brake Problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72super20 · 01-07-2003, 04:47 PM

I recently put a new power booster on my 72 Cheyenne Super 20. The brakes were stronger.....but now they tend to build up pressure and not release it. The front wheels will totally lock until I bleed off the pressure.

I did have to back the brake light adjustement off about a 1/4 inch after installing the booster.

Is it possible that the booster and master cylinder for the 72 - 3/4 ton can have different possible combinations?? Is there any type of check valve in the brake system that could cause the pressure to not release??

Gordo · 01-07-2003, 05:09 PM

If the piston within the master is being held from returning ALL the way back you will have the problem you descibe. Could be the push pin needs to be adjusted, some of them have a adjustment on the tip, this would also explain why you have to adjust the brake light switch. Could be the booster was to fit a drum brake master?

crazy longhorn · 01-07-2003, 05:12 PM

You might try loosening the master where it bolts to the booster to see if that relieves the drag on the front brakes. If that works, a shim tween the master & booster should set you up. Good luck......crazyL

72super20 · 01-07-2003, 05:27 PM

Thanks, I will give the shim a try.

Love the site!!! Rhode Island and Connecticut...Who would have thought I would get my answers from there?

How do you find or keep those 30 year old trucks from rusting up there?

Gordo · 01-07-2003, 05:33 PM

How do you find or keep those 30 year old trucks from rusting up there?
Answer,
You don't!
Where do you call home?

crazy longhorn · 01-07-2003, 06:19 PM

72super 20, if you find an adjuster, by all means use it! If you need to shim, a 2 or 3 washers will be a temp deal(carefully). By shim, I should be clear........it should be the shape of the back of the master, & have 3 holes in it(2 for the studs &1 for the pin). Gordo......up here we cant stop the trucks from rusting, we just have to try to slow the process down!

Home is in the garage........when the wifey is on the "warpath"

DennyB · 01-07-2003, 06:28 PM

Also check the brake light switch for proper adjustment.
It can hold the piston from returning completely.
If you altered it in any way I would check that first, then onto to what was stated above.

Denny

Ed ke6bnl · 01-08-2003, 04:53 AM

Check to see that you do not have the check valve in the m/c we did and the front discs did not release without relieving brake flluid pressure at the m/c. Just a suggestion worked for our case thanks to the help of this group. Ed ke6bnl

01-07-2003, 04:47 PM	#1
72super20 Registered User Join Date: Jan 2003 Posts: 2	Front Disk Brake Problem I recently put a new power booster on my 72 Cheyenne Super 20. The brakes were stronger.....but now they tend to build up pressure and not release it. The front wheels will totally lock until I bleed off the pressure. I did have to back the brake light adjustement off about a 1/4 inch after installing the booster. Is it possible that the booster and master cylinder for the 72 - 3/4 ton can have different possible combinations?? Is there any type of check valve in the brake system that could cause the pressure to not release?? __________________ Big Rick 1972 Cheyenne Super 20

01-07-2003, 05:09 PM	#2
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	If the piston within the master is being held from returning ALL the way back you will have the problem you descibe. Could be the push pin needs to be adjusted, some of them have a adjustment on the tip, this would also explain why you have to adjust the brake light switch. Could be the booster was to fit a drum brake master? __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

01-07-2003, 05:12 PM	#3
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	You might try loosening the master where it bolts to the booster to see if that relieves the drag on the front brakes. If that works, a shim tween the master & booster should set you up. Good luck......crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

01-07-2003, 05:27 PM	#4
72super20 Registered User Join Date: Jan 2003 Posts: 2	Thanks, I will give the shim a try. Love the site!!! Rhode Island and Connecticut...Who would have thought I would get my answers from there? How do you find or keep those 30 year old trucks from rusting up there? __________________ Big Rick 1972 Cheyenne Super 20

01-07-2003, 05:33 PM	#5
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	How do you find or keep those 30 year old trucks from rusting up there? Answer, You don't! Where do you call home? __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

01-07-2003, 06:19 PM	#6
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	72super 20, if you find an adjuster, by all means use it! If you need to shim, a 2 or 3 washers will be a temp deal(carefully). By shim, I should be clear........it should be the shape of the back of the master, & have 3 holes in it(2 for the studs &1 for the pin). Gordo......up here we cant stop the trucks from rusting, we just have to try to slow the process down! Home is in the garage........when the wifey is on the "warpath" __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

01-07-2003, 06:28 PM	#7
DennyB Led Sled! Discs R 4 ME! Join Date: Jan 2001 Location: Toms River, NJ, USA (Transplanted Hoosier) Posts: 7,327	Also check the brake light switch for proper adjustment. It can hold the piston from returning completely. If you altered it in any way I would check that first, then onto to what was stated above. Denny __________________ "Never ride faster than your Angel can fly" I.M.O.M,W,J&C Patriot Guard Rider

01-08-2003, 04:53 AM	#8
Ed ke6bnl Registered User Join Date: Mar 2002 Location: Agua Dulce, Ca. usa Posts: 179	Check to see that you do not have the check valve in the m/c we did and the front discs did not release without relieving brake flluid pressure at the m/c. Just a suggestion worked for our case thanks to the help of this group. Ed ke6bnl __________________ Ed ke6bnl Agua Dulce 70 S.E. Los Angeles 70 Chevy short bed 1948 F3 ford pu 1949 F1 stock V8 flathead 3 on floor 1950 F1 pu street rod 1948 F6 Ford Dually/350sbc no bed stock trans&rear 1972 El Camino 4" chop 1953 Chevy 3100 2b daily driver 1970 SB 4X4 400ci 6in lift

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